Arctic Methane and Tipping Points

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Massive methane release from thawing permafrost and undersea sediments is one of the best known Climate Tipping Points, featuring in newsstories and scientificreports and triggering fears by some of ‘runaway‘ warming. Methane is a potent greenhouse gas which is around 34 times as powerful as carbon dioxide over ~100 years, and so a rapid release of methane could significantly amplify global warming. But are there methane tipping points, and how close might we be to them?

There are two main sources of methane that scientists are worried about: methane trapped in ice below the seafloor (known as ‘Methane Hydrates’ or ‘Clathrates’), and methane generated by the thawing and decomposition of Permafrost.

Huge areas of soil around the Arctic are frozen all year round and so are known as permafrost. As these areas are so cold any organic matter that accumulates from plants tends not to rot, gradually building up thick soils known as ‘Yedoma’ that are full of organic carbon. These soils may contain as much as nearly twice the carbon which is currently in the atmosphere.

Methane hydrates occur in sediments both on land and the seafloor, and are made of methane molecules from rotting organic matter getting trapped within ice crystals. It looks just like ice, but it can catch fire! Methane hydrates can only form at very specific temperatures and pressures, and warming can destabilise them and cause the methane to be released.

Both of these methane sources are vulnerable to the effects of Arctic sea ice loss triggering rapid Arctic warming- another Climate Tipping Point discussed in a previous blogpost. The Arctic is warming up much faster than the global average as sea ice retreats, and this is warming up regions with large permafrost and methane hydrate deposits. This would speed up methane release from these deposits, which would add to global warming and therefore Arctic warming in a positive feedback loop, making Arctic methane another potential Climate Tipping Point.

Although methane tipping points may not be as catastrophic as has been feared, passing these imminent tipping points will still trigger the steady release of methane from permafrost and methane hydrates and will help to amplify global warming in the coming centuries.